JPH02113032A - Polyester film coated with amino-functional silane primer, which can be extrusion coated, and extrusion-coated laminate made thereof - Google Patents

Abstract

PURPOSE: To provide a polyester film requiring no separate application of a primer by forming a water-soluble primer coating material containing a hydrolysate of amino functional silane on a drawn polyester film.

CONSTITUTION: This polyester film is formed by containing a dry residue of the hydrolysate of an aminosilane compound of the formula (R¹)_aSi(R²)_b(R³)_c [R¹ is a group having at least one primary amino group; R² is a 1-8C alkoxy or the like; R³ is a 1-8C alkyl or the like; (a), (b) are 1 or more, and (c) is 0 or more with a+b+c=4] in a primer film having a primer coating material [e.g.: N-2-(aminoethyl)-3-aminopropyltrimethoxysilane or the like] applied to at least one surface of a drawn polyester film (e.g.: polyethylene terephthalate) in 0.10×10^-6-20×10^-6 pounds (about 0.49-98 mg/m²) per feet² of the film surface on the basis of the dry weight.

COPYRIGHT: (C)1990,JPO

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a primer-coated stretched polyester film having a primer coating formed by coating on at least one side a water-soluble primer coating containing a hydrolyzate of an amino-functional silane. Regarding. This coating makes the surface of the polyester film more receptive to extrusion coating of other polymeric film materials such as polyolefins.

[Conventional technology]

Stretched polyester films, especially biaxially oriented films, made of polyethylene terephthalate (PET) have been widely used as packaging materials or as supports for microfilms, electrophotographic films, proofing films, etc. This film has good optical clarity and toughness, making it highly suitable for such applications.

The main uses for PET films include lamination with other polymers as well as paper or foils. To give PET film heat-sealability or adhesiveness to other materials such as aluminum foil, to increase its thickness (bulk) or rigidity, or to give this film properties that cannot be obtained with PET alone. In addition, PET films are often extrusion coated with polyethylene or ethylene copolymers.

Unfortunately, the surface of PET film is not very receptive to extrusion coating with other polymers, and many primer coatings are used to apply it to the surface of polyester film to improve its adhesion to various materials. Traditionally known. Examples of such coatings include compositions that utilize vinylidene chloride polymers as the main component (U.S. Pat. No. 2,698,240), compositions that utilize thermosetting acrylic or methacrylic polymers (U.S. Pat. 819,773).

U.S. Patent Nos. 3,563,942 and 3,779
It is also known to use certain water-dispersible copolyesters as adhesives in laminating sheets of polyester film together or with sheets of nylon film, as described in US Pat. be.

More commonly, solvent-based polyurethane adhesives and polyethyleneimine primers are used, but these are associated with solvent volatilization and safety issues. It has also been proposed to use corona discharge treatment, with or without primer application, to obtain adhesion between extruded films.

A typical extrusion coating operation involves taking PET film purchased from a film manufacturer, corona discharge treatment by the converter, applying a primer to the corona treated film, and applying a primer to the corona treated film.
After drying the primer, the film is extrusion coated with another polymer. Since a separate coating process of applying a primer to the film is required, additional expensive coating equipment must be installed, and this process adversely affects production speed. Furthermore, if a solvent-based primer is required, additional safety and environmental pollution prevention equipment will be required, and various regulatory obligations will be imposed, creating another burden.

For the above reasons, extrusion coating can be applied as is without separate primer application or corona discharge treatment.
It would be advantageous for processors to have access to film that has already been corona treated or primed, or directly extruded by electrical discharge treating or priming the film within the production line during film production. It is also possible to produce coatable films,
This would be advantageous in terms of avoiding the costs and problems mentioned above.

For the in-line primer application process, the primer paint is water-based for safety and health reasons and is recyclable (i.e., scraps of primed film are mixed with new polymer to form a film). It does not cause excessive yellowing or physical property deterioration when recycled by re-extrusion (this regeneration is required due to low conversion efficiency in in-line processing), and does not cause the film to stick or bronck. Ideally, it would be hard enough to be rolled into a roll without any stiffness (this is a necessary property for a directly extrusion coatable film).

Direct extrusion coatable polyester films are disclosed in US Pat. No. 4,410,600. Disclosed in this patent is a biaxially oriented PET film coated in-line with a crosslinked styrene-maleic anhydride copolymer. However, this primer coated film still requires corona discharge treatment before extrusion coating.

It is known to use a silane coupling agent to improve bonding between polyethylene sheets and polyester sheets. For example, E, Plueddes+ann
Author: “Joining using cambling agents, 4 PIenu+w
As disclosed in Press (1985),
Polyester sheets primed with either vinyltrimethoxysilane or chloropropyltrimethoxysilane and polyethylene sheets were laminated using true melt adhesives such as ethylene/vinyl acetate terpolymers or elastomeric polyesters. In addition, N-2-aminoethyl-3-aminopropyltrimethoxysilane (Z-6 from Dow Chemical Company)
U.S. Pat. No. 4.66 discloses the use of ionomer resins (salts of copolymers of ethylene and methacrylic acid) to glass and polycarbonate sheets using ionomer resin (commercially available under the trade name 020) as a primer coating.
No. 3,228. Related silanes, such as N-3-aminopropyltrialkoxysilane, are also known to enhance the adhesion of polyurethane films to glass substrates, as disclosed in European Patent Application No. 171.917.

[Problem to be Solved by the Invention] The above prior art disclosure discloses that polyethylene, ethylene copolymers and ionomers or other polymer films can be prepared without a separate primer coating or a separate corona discharge treatment. None have addressed the issue of coatability when extrusion coating films directly.

It is therefore an object of the present invention to provide a stretched polyester film that can be directly extrusion coated with other polymers without the need for a separate primer coating or corona discharge treatment.

Another object of the present invention is to provide a polyester film having a primer coating that allows recycling of primer-coated film waste without excessive yellowing or property deterioration of the recycled polymer.

Since most conventional primer paints use volatile solvents, it is necessary to provide ancillary facilities such as solvent treatment equipment, worker protection equipment, and waste solvent disposal equipment.

It is therefore a further object of the present invention to develop a water-based primer coating that can be used in most existing systems without the need for expensive ancillary equipment.

SUMMARY OF THE INVENTION It is an object of the present invention to apply a hydrolyzate of an amino-functional silane to a stretched polyester film as a primer, thereby making the film susceptible to direct extrusion coating with other polymers. This can be achieved by providing a primed polyester film that is receptive to

Amino-functional silane compounds useful as primers for the purposes of this invention are those shown below in general 2 in their pre-hydrolyzed state.

(R') mst (R'') b (R') c In the above formula, " is a functional group having at least one primary amino group; Q
l is a hydrolyzable group such as a lower alkoxy group, acetoxy group or halogen; R2 is a non-reactive, non-hydrolyzable group such as a lower alkyl group or phenyl group; a is 1 or more; b is 1 or more, C is 0 or 1 or more, and a+b+c=4.

Generally, the amino-functional silane compound is hydrolyzed in water and applied to one or more surfaces of the stretched polyester film by any conventional coating method, such as spray coating or roll coating. When the silane primer coating dries, the primer coated polyester film
Receptive to direct extrusion coating with one or more polymers. Extrusion coating can be performed by any conventional method. The primer coating functions to bond the polyester film and extruded film to form a laminate.

In its broadest sense, the present invention relates to a film comprising a stretched polyester film provided with an effective amount of a primer coating to render the film amenable to direct extrusion coating with one or more polymers. In the state before hydrolysis, this primer has the following general formula: % formula % () [wherein " is a functional group having at least one primary amino group; R3 is a hydrolyzable group; a is 1 or more, b is 1 or more,
C is O or more, and a+b+C=4].

In its broadest sense, the invention also relates to a laminate comprising a stretched polyester film, a primer coating, and one or more directly extruded polymer layers, which primer coating, in its pre-hydrolyzed state, has the following general formula: % formula % () [In the formula, R1 is a functional group having at least one primary amino group, R1 is a hydrolyzable group, and R3 is a non-reactive and non-hydrolyzable group, respectively; 1 or more, b is 1 or more, C is 0 or more, and a+b+c=4].

[Function] Silanes become water-soluble or water-dispersible after hydrolysis, but amino-functional silane compounds in particular become water-soluble. It has also been found that direct extrusion coating polymers can provide good adhesion to polyester films. They also found that scrap polyester film primed with aminosilane paint could be recycled.

Amino-functional silane compounds which can be used as primers for the purposes of the present invention are those represented by the following general formula in their pre-hydrolyzed state.

(R'), 5i(R")b(R')c In the above formula, llI is a functional group having at least one primary amino group; R1 is a lower alkoxy group having 1 to 8 carbon atoms, an acetoxy group, and a halogen a hydrolyzable group selected from the group consisting of; R3 means a non-reactive, non-hydrolyzable group selected from the group consisting of a lower alkyl group having 1 to 8 carbon atoms and a phenyl group; is 1 or more, b is 1 or more, C is O or more, and a+b+c=4.

Examples of aminosilane compounds that fit the above general formula include N
-2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3
-aminopropyltriethoxysilane, 4-aminobutyltriethoxysilane, 4-aminobutyldimethylmethoxysilane, and p-aminophenyltrimethoxysilane. A preferred silane compound is N-2-aminoethyl)-3-aminopropyltrimethoxysilane represented by the following formula.

HJ(CHt)□NH(CHri ssi (OCRs)
3. The hydrolyzed aminosilane may be applied to the polyester film as an aqueous solution at any suitable stage during film production (i.e., before or during the stretching operation), or it may be applied to the stretched film after production. can. The resulting primed polyester film was found to exhibit adhesion to polymeric films extrusion coated onto the film.

The primer paint used in the present invention contains about 0 aminosilane.
．． It is prepared by mixing with water to a concentration within the range of 2-6%. Optionally, at least one hydrolyzable group of the silane may be replaced by a silanol group (S
iOH). The hydrolysis product of the aminosilane compound has a partially hydrolyzed cyclic structure,
The amino group probably forms an ionic bond with the silicon portion of the molecule. That is, in this specification, the term "hydrolyzate" may also mean a product having such a partially hydrolyzed structure.

A preferred stretched polyester film for the purposes of the present invention is polyethylene terephthalate, but with a glycol component such as ethylene glycol or bucundiol or mixtures thereof and terephthalic acid, or terephthalic acid and other dicarboxylic acids such as isophthalic acid, diphenic acid or sebacic acid. The present invention is equally applicable to any film based on a crystalline polyester obtained by polycondensation with a dicarboxylic acid component such as a mixture with an acid or a dicarboxylic acid component such as a polyester-forming derivative thereof. Such polyester resins are manufactured by methods well known in the art.

Film production can also be carried out using techniques well known in the art and using well known equipment.

For example, polyester is melted and extruded into an amorphous sheet onto a rotating casting drum with a polished surface to form a cast sheet of the polymer. Thereafter, the obtained film is stretched in either the extrusion direction (longitudinal direction) or the direction perpendicular to the extrusion direction (transverse direction) in the case of a -axially stretched film.
direction, and in the case of biaxially stretched films, in two directions,
That is, the film is stretched in both the length and width directions. The initial stretch, which gives the film strength and toughness, is approximately 3.0 to 5.
It can be within the range of 0 times.

The hydrolyzed aminosilane primer coating of the present invention in aqueous solution can be used in three stages during film manufacture, namely casting of an amorphous sheet and initial stretching as disclosed in GB 1,411,564, for example. pre-stretching steps at points between Can be applied in-line at any post-stretch stage. Typically, the heat applied to the film during stretching or the final conditioning stage is sufficient to evaporate water and other solvents. Although the primer coating dries, a separate drying step may be required if a primer coating is applied after such a heating step.

In a preferred embodiment, the primer coating is applied after the film has been uniaxially stretched, that is, after the film has been stretched in one direction but before it is stretched in a direction perpendicular to this direction. In another preferred embodiment, the polyester film is first stretched in the machine direction before coating. In this preferred embodiment, after longitudinal stretching, the film is coated with a primer by any coating method known in the art.6 For example, coating can be done by roll coating, spray coating, slot coating, or dip coating. can. In a preferred embodiment, the primer is applied to the polyester film by gravure roll coating. The -axially oriented film may also be corona discharge treated with a corona discharge device prior to coating, as is known in the art. Corona discharge treatment reduces the hydrophobicity of the polyester film surface, allowing the water-based primer paint to better wet the film surface and improving the adhesion of the primer coating to the surface.

The hydrolyzed aminosilane of the present invention can be applied to the film as an aqueous solution containing the aminosilane hydrolyzate at a concentration of about 0.2 to 6% by weight. About 0.2% by weight of a weak # (eg, acetic acid, phosphoric acid, etc.) is then added to promote hydrolysis. The preferred concentration of hydrolyzed aminosilane is within the range of about 0.25-2.5% by weight.

The preferred concentration is about 0.10 x 10 - which is the target deposition layer.
The concentration is such that the primer coating yields a final dry primer coating coverage of 'Ib/ft' (0.4 lb/ft). If the coating is applied as a polyurethane powder, the coating weights can be quite high, with dry coating weights of 10xlO-'lb#t'' (49 .mu./po) or higher giving good results.

The primer coating of the present invention can be applied to one or both sides of the film. Alternatively, if coated on one side, another coating can be applied to the opposite side, such as a thermoset acrylic or methacrylic resin coating as described in U.S. Pat. No. 4,214.035. Alternatively, a coating to which the aminosilane primer coating described above adheres, formed from another primer coating such as the thermoset acrylic coating described in U.S. Pat. An aminosilane primer paint can also be applied over this coating.

The primer paint of the present invention may further contain other components as long as they do not inhibit the adhesion promoting effect of the hydrolyzed aminosilane compound. Examples of such other components include:
Contains small amounts of colloidal silica, dyes, pH regulators, wetting agents, etc. The primer coating is present as a continuous coating on the film surface. Continuous coating also includes the case where the primer may form multiple islands or separate coating sections.

Film waste coated with the primer coating of the present invention, which is produced as scrap during the manufacturing process, is crushed, mixed with new polyester, remelted and reextruded to produce stretched film. The polyester film thus obtained, which contains a significant amount of recycled primer-coated waste, exhibits only a slight deterioration of its physical properties due to the inclusion of paint as an impurity, and is also less colored, i.e., according to the present invention. Primed films offer commercial advantages to film manufacturers over many other primed films. Other film examples include U.S. Pat. No. 2,627.088 and U.S. Pat.
There is a film coated with a vinylidene chloride-containing polymer disclosed in No. 0 as a primer, but this shows a tendency for physical properties to deteriorate and discoloration when recycled as described above.

The laminate can be produced by the well-known extrusion coating process, in which molten sheets of polymer are successively deposited on the primed side of a moving web of polyester film. Laminates of polyester and polyethylene, ethylene-vinyl acetate copolymers, polyvinyl alcohol, polyvinyl acetate, ionomers and other polymers can be readily produced by extrusion coating techniques.

Although it cannot be determined with certainty that polyethylene extrusion-coated laminates of PE1' film exhibit particularly useful properties such as good heat-sealability and good adhesion to other materials such as aluminum foil, the amino groups in the primer It is thought that the primer reacts with the heated and oxidized polyethylene when it is extruded onto the PET film, resulting in a strong bonding of the primer to the polyethylene.

The thickness of polyester films used in the present invention may generally range from about 0.25 to 10 mils or more.

The following examples are illustrative of the invention.

[Example] 2-ball stopper x manufacturing method N-2-aminoethyl)-3-aminopropyltrimethoxysilane (AE-APTMS) (from Dow Corning as Z-6020 and from Union Carbide as A- 1120) or N-3-aminopropyltrimethoxysilane (APTMS) at approx.
It was dispersed in ordinary tap water to a concentration of 25-1.5% by weight of AE~^PTMS (or other aminosilane). 0.2% by weight to accelerate hydrolysis
of acetic acid was added.

The polyethylene terephthalate polymer was melted and extruded through a slot die onto a rotating casting drum maintained at a temperature of about 20°C. The melt solidified to obtain a cast sheet. The cast sheet was stretched in the machine direction at a draw ratio of about 3.5:1 while maintaining the temperature at about 80°C.

After the longitudinally stretched film was subjected to corona discharge treatment using a corona discharge device, the aqueous solution of the hydrolyzed aminosilane compound was applied using an inverted gravure roll.

The longitudinally stretched, corona discharge treated and primed film was dried at a temperature of approximately 100°C. Thereafter, the film was stretched in the transverse direction at a stretch ratio of about 3.91 to obtain a biaxially stretched film. The stretched film had a thickness of about 0.5-3 mils.

This biaxially stretched film was then heat set at a maximum temperature of 230°C. The dry coverage of the primer coating is approximately 0.50 x 10-hlb per square foot of film (
2.4mg/rr? )Met.

Example 1] A polyethylene terephthalate film was produced, stretched, and coated with a primer by the method described in the above film production method. This film was coated with an aqueous aminosilane coating shown in Table 1 below. A 100-foot length of primer coated film is prepared for each) primer coating composition, wound into a roll into a composite roll, and the roll is sent to an extrusion coating machine to coat approximately 1 mil thick low-density polyethylene (LDPE). ) (ASR resin with melt index of 14) was extrusion coated. The melt temperature was about 620° C. below (326° C.), the extrusion die height above the film was about 8 inches (20 cm), and no further corona discharge treatment or primer application was performed during extrusion coating.

Table 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Silane.

Uncoated control sample 0.25χAE-APTMS" 0.5χ AE-APTMS" 1.0χ AE-APTMS" 1.5χ AE-APTMS" 0.5χ APTMS" 1.0χ APTMS"0.27×10-' 0. 55xlO-'1.10X10-'1.64X10-'0.41XlO-'0.82X10-' AST? 0.09 lb/in as measured using l tests D882 and E4.

The adhesion of the polyethylene to the films of Runs N2-8 was so good that even when peeling was attempted for a peel test, the two layers could not be peeled off. PET/LD can also be reduced by hot water, toluene or tetrahydrofuran.
It was not possible to perform peeling at the PH interface. A
Adhesion was excellent when both PTMS (N-3-aminopropyltrimethoxysilane) and AE-APTMS (N-2(aminoethyl)-3-aminopropyltrimethoxysilane) were applied.

A polyethylene terephthalate film was prepared, stretched, and primed as described in the film preparation method above. The film thickness was 0.5 mil. The film was coated with the aminosilane aqueous coating shown in Table 2. 10 lengths for each primer paint composition
0 feet of primed film was produced and rolled into a composite roll. The roll was sent to an extrusion coating machine to coat 5U, an ionomer resin approximately 0.75 mil thick.
RLYN@1652 was extrusion coated. The melting temperature is approximately 5
Half of each sample was corona discharge treated at 2.5 KVA before extrusion coating, and the other half was not corona discharge treated. Another composite roll of the same film was Low density polyethylene (LDPE) resin Norchem@1014 (0.75 mil thickness, melt extrusion temperature 625 below = 329°C) was extrusion coated. As with the coating of 5tlRLYN@, half of the samples were coated with corona. discharge treated and the other half not corona treated using an Instron tester, As/7M D88
Peel strength was measured according to 2 and E4. In addition, during the extrusion coating operation, a piece of untreated polyester film was inserted between the ends of the two layers to be laminated, and two pieces of untreated polyester film were inserted for peel testing.
A non-adhesive area was formed from which the layers could be peeled off.

Example 9 Example 10 Example 11 Example 12 Example 13 Example 14 Example 15 Example 16 Example 17 Example 18 Example 19 Example 20 Example 21 Example 22 Example 23 Example 24 Example 25 Example 26 Example 27 Male'1 Table 0.25χ AE-APTMS 0025χAE-APTMS O650χ AE-APTMS 0.50χ AE-APTMS 1.00χ AE-APTMS 1899χ AE-APT gate S 1.50χ AE-＾PT Ah " Uncoated and uncoated None Yes No Yes Yes Yes No Yes 2.62 2.84 2.17 4.25 2.42 2.42 2.50 2.54 3.19 2.89 2.24 3.13 1.58 1 .79 1.94 2.19 1.03 0.02 1.05 1.23 1.22 1.43 1.36 1.23 1.30 1.41 1.42 1.28 1.43 1.25 1.18 1.23 1.29 1.67 1.27 0.44 0.08 1.03 For uncoated PET film and copolyester coated film, 5URIJN for polyester film
To obtain some adhesion of @1652 and Norchsm @1014, corona discharge treatment is necessary before extrusion coating. Even with corona discharge treatment, the adhesion to uncoated PET and copolyester-coated films does not improve adhesion to films coated with aminosilane according to the present invention, and corona discharge treatment of aminosilane-coated films is not necessary. There was no difference in adhesion.

Both AE-APTMS and APTMS had sufficiently good adhesion even at a low concentration of about 0.25% by weight.

From the foregoing, it is clear that the present invention provides extrusion coatable primer coated films and extrusion coated laminates that fully satisfy the objects and advantages set forth above. Although described above, many changes, modifications and variations will be apparent to those skilled in the art based on the above description, and all such changes, modifications and variations are intended to be included within the scope of this invention. be.

Claims (17)

[Claims] (1) On at least one side of the stretched polyester film,
A film having a coating formed by applying a primer coating at an amount effective to improve the adhesion of one or more extrusion coated polymers to the polyester film, wherein the primer coating is In the state, the following general formula: (R^1)_aSi(R^2)_b(R
^3)_c [wherein R^1 is a functional group having at least one primary amino group; R^2 is selected from the group consisting of a lower alkoxy group having 1 to 8 carbon atoms, an acetoxy group, and a halogen group Hydrolyzable group; R^3 means a non-reactive, non-hydrolyzable group selected from the group consisting of a lower alkyl group having 1 to 8 carbon atoms and a phenyl group; a is 1 or more , b is 1 or more, c is 0 or more, and a + b + c = 4]. . (2) The film according to claim 1, wherein the hydrolyzable group is an alkoxy group selected from the group consisting of methoxy and ethoxy. 3. The film of claim 1, wherein the amino functional group is selected from the group consisting of primary amino groups, diamines, and triamines. (4) The aminosilane compound is N-2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and N-2aminoethyl-2-
2. The film of claim 1, wherein the film is selected from the group consisting of aminoethyl-3-aminopropyltrimethoxysilane. (5) The film according to claim 1, wherein the stretched polyester film is polyethylene terephthalate. (6) The film according to claim 5, wherein the film is a biaxially oriented polyethylene terephthalate film. (7) The film is obtained by melt-extruding a substantially amorphous polyester film and then sequentially stretching and orientating the film in two directions, with the film being oriented in the first direction. Either before stretching, after stretching in the first direction and before stretching in a second direction perpendicular thereto, or after stretching in two directions, the primer coating is applied to the film as an aqueous solution. 7. The film according to claim 6, wherein the film is coated. (8) The film according to claim 7, wherein the film is subjected to a corona discharge treatment before applying the primer paint. (9) The film according to claim 7, wherein the primer coating is applied after the film is stretched in the first direction and before the film is stretched in a second direction perpendicular to the first direction. (10) The primer paint contains N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and N-2-aminoethyl-2
8. The film of claim 7, which is an aqueous dispersion of an aminosilane compound selected from the group consisting of -aminoethyl-3-aminopropyltrimethoxysilane. (11) The primer coating has a dry weight of about 0.10 x 10^-^6 per square foot of film surface.
~20×10^-^6 pounds (approx. 0.49-98mg/
11. The film according to claim 10, coated with a coverage of m^2). (12) The primer-coated film according to claim 1, further comprising another polymer layer adhered to the primer-coated surface of the primer-coated film. 13. The film of claim 12, wherein the polymer is extrusion coated onto a primer coated film. 14. The film of claim 13, wherein the extrusion coated polymer is a polyester or copolyester. 15. The film of claim 13, wherein the extrusion coated polymer is a polyolefin. 16. The film of claim 15, wherein the extrusion coated polymer is selected from polyethylene and ethylene copolymers. (17) The extrusion coated polymer is SURLYN^
14. The film of claim 13, wherein the film is selected from the group consisting of ionomers, ethylene-vinyl acetate copolymers, polyvinyl alcohol, and polyvinyl acetate.